Colorado tied Calgary with 73 points and moved within a point of Anaheim and St. Louis for the second wild card.
Johnny Gaudreau was tossed after drawing a high-sticking penalty on Colorado's Blake Comeau. Gaudreau was given an unsportsmanlike minor penalty on the play and then assessed a game misconduct after arguing with the officials from the penalty box.
Colorado took control with a four-goal flurry in the second period that turned a 2-0 deficit into a two-goal lead. MacKinnon's 29th midway through the period started it, Zadorov tied it 1:08 later, and Barrie gave Barrie gave the Avs a 3-2 lead with his seventh goal at 12:41.
Nieto made it 4-2 with 1:18 to go when Carl Soderberg threaded a pass through two defensemen to the front of the net for an easy tap-in.
Duncan Siemens sealed it when he scored into an empty net with 17 seconds left in the game for his first NHL goal.
The Flames capitalized on a pair of Colorado turnovers to take an early two-goal. Backlund scored a short-handed goal at 14:19 of the first, and Frolik made it 2-0 with his 10th goal 2:41 into the second.
Colorado was 1 of 7 on the power play. ... Flames D Nick Shore, acquired from Ottawa on Monday, was scratched due to illness. ... The Avalanche recalled G Spencer Martin from the AHL to serve as Varlamov's backup. Jonathan Bernierand Andrew Hammond are in the concussion protocol. ... Calgary is 6-4-1 on the second night of back-to-back games. ... Comeau and Soderberg had two assists each for Colorado.
Flames: Host the New York Rangers on Friday night.
Avalanche: Host Minnesota on Friday night.